package com.algorithms.avltree;

import java.util.ArrayList;

/**
 * @author itjunjun  2021/6/8 10:03
 */
public class AVLTree<K extends Comparable<K>, V> {

    private class Node {
        public K key;
        public V value;
        public Node left, right;
        public int height;

        public Node(K key, V value) {
            this.key = key;
            this.value = value;
            left = null;
            right = null;
            height = 1;
        }
    }

    private Node root;
    private int size;

    public AVLTree() {
        root = null;
        size = 0;
    }

    public int getSize() {
        return size;
    }

    public boolean isEmpty() {
        return size == 0;
    }

    //判断是否为二分搜索树
    public boolean isBST() {
        ArrayList<K> keys = new ArrayList<>();
        inOrder(root, keys);
        for (int i = 0; i < keys.size(); i++) {
            if (keys.get(i - 1).compareTo(keys.get(i)) > 0) {
                return false;
            }
        }
        return true;
    }

    private void inOrder(Node node, ArrayList<K> keys) {
        if (node == null) {
            return;
        }
        inOrder(node.left, keys);
        keys.add(node.key);
        inOrder(node.right, keys);
    }

    //判断是否为平衡二叉树
    public boolean isBalanced() {
        return isBalanced(root);
    }

    private boolean isBalanced(Node node) {
        if (node == null) {
            return true;
        }
        int balancedFactor = getBanlanceFactor(node);
        if (Math.abs(balancedFactor) > 1) {
            return false;
        }
        return isBalanced(node.left) && isBalanced(root.right);
    }

    //传入一个节点返回该节点对应的高度值
    private int getHeight(Node node) {
        if (node == null) {
            return 0;
        }
        return node.height;
    }

    //获得node的平衡因子
    private int getBanlanceFactor(Node node) {
        if (node == null) {
            return 0;
        }
        return getHeight(node.left) - getHeight(node.right);
    }

    //右旋转，返回旋转后的新的根节点x
    //           y                             x
    //         /  \                           / \
    //        x    T4       右旋转           z    y
    //      /  \          -------->       /  \  / \
    //     z    T3                       T1  T2 T3 T4
    //    / \
    //  T1   T2
    private Node rightRotate(Node y) {
        Node x = y.left;
        Node T3 = x.right;
        //旋转
        x.right = y;
        y.left = T3;
        //更新height
        y.height = Math.max(getHeight(y.left), getHeight(y.right)) + 1;
        x.height = Math.max(getHeight(x.left), getHeight(x.right)) + 1;
        return x;
    }

    //           y                             x
    //         /  \                           / \
    //        T1   x       左旋转             y   z
    //           /  \     -------->        / \  / \
    //          T2   z                   T1  T2 T3 T4
    //              / \
    //            T3   T4
    private Node leftRotate(Node y) {
        Node x = y.right;
        Node T2 = x.left;
        //左旋转
        x.left = y;
        y.right = T2;
        //更新高度
        y.height = Math.max(getHeight(y.left), getHeight(y.right)) + 1;
        x.height = Math.max(getHeight(x.left), getHeight(x.right)) + 1;
        return x;
    }

    // 向二分搜索树中添加新的元素(key, value)
    public void add(K key, V value) {
        root = add(root, key, value);
    }

    // 向以node为根的二分搜索树中插入元素(key, value)，递归算法
    // 返回插入新节点后二分搜索树的根
    private Node add(Node node, K key, V value) {
        if (node == null) {
            size++;
            return new Node(key, value);
        }
        if (key.compareTo(node.key) < 0) {
            node.left = add(node.left, key, value);
        } else if (key.compareTo(node.key) > 0) {
            node.right = add(node.right, key, value);
        } else {// key.compareTo(node.key) == 0
            node.value = value;
        }
        //更新height
        node.height = 1 + Math.max(getHeight(node.left), getHeight(node.right));
        //计算平衡因子
        int balanceFactor = getBanlanceFactor(node);
        if (Math.abs(balanceFactor) > 1) {
            System.out.println("unblanced:" + balanceFactor);
        }
        //维护平衡
        // LL 和 RR 型
        if (balanceFactor > 1 && getBanlanceFactor(node.left) > 0) {
            return rightRotate(node);
        }
        if (balanceFactor < -1 && getBanlanceFactor(node.right) <= 0) {
            return leftRotate(node);
        }
        //LR
        if (balanceFactor > 1 && getBanlanceFactor(node.left) < 0) {
            node.left = leftRotate(node.left);
            return rightRotate(node);
        }
        //RL
        if (balanceFactor < -1 && getBanlanceFactor(node.right) > 0) {
            node.right = rightRotate(node.right);
            return leftRotate(node);
        }
        return node;
    }

    // 返回以node为根节点的二分搜索树中，key所在的节点
    private Node getNode(Node node, K key) {

        if (node == null) {
            return null;
        }
        if (key.equals(node.key)) {
            return node;
        } else if (key.compareTo(node.key) < 0) {
            return getNode(node.left, key);
        } else { // if(key.compareTo(node.key) > 0)
            return getNode(node.right, key);
        }
    }

    public boolean contains(K key) {
        return getNode(root, key) != null;
    }

    public V get(K key) {

        Node node = getNode(root, key);
        return node == null ? null : node.value;
    }

    public void set(K key, V newValue) {
        Node node = getNode(root, key);
        if (node == null) {
            throw new IllegalArgumentException(key + " doesn't exist!");
        }
        node.value = newValue;
    }

    // 返回以node为根的二分搜索树的最小值所在的节点
    private Node minimum(Node node) {
        if (node.left == null) {
            return node;
        }
        return minimum(node.left);
    }

    // 删除掉以node为根的二分搜索树中的最小节点
    // 返回删除节点后新的二分搜索树的根
    private Node removeMin(Node node) {

        if (node.left == null) {
            Node rightNode = node.right;
            node.right = null;
            size--;
            return rightNode;
        }

        node.left = removeMin(node.left);
        return node;
    }

    // 从二分搜索树中删除键为key的节点
    public V remove(K key) {

        Node node = getNode(root, key);
        if (node != null) {
            root = remove(root, key);
            return node.value;
        }
        return null;
    }

    /**
     * 这个方法主要是将删除了对应节点后的根节点进行保存，然后检查这个节点的平衡因子，再进行旋转保持平衡
     *
     * @param node
     * @param key
     * @return
     */
    private Node remove(Node node, K key) {

        if (node == null) {
            return null;
        }
        Node retNode;
        if (key.compareTo(node.key) < 0) {
            node.left = remove(node.left, key);
            retNode = node;
        } else if (key.compareTo(node.key) > 0) {
            node.right = remove(node.right, key);
            retNode = node;
        } else {   // key.compareTo(node.key) == 0
            // 待删除节点左子树为空的情况
            if (node.left == null) {
                Node rightNode = node.right;
                node.right = null;
                size--;
                retNode = rightNode;
            }
            // 待删除节点右子树为空的情况
            else if (node.right == null) {
                Node leftNode = node.left;
                node.left = null;
                size--;
                retNode = leftNode;
            } else {
                // 待删除节点左右子树均不为空的情况

                // 找到比待删除节点大的最小节点, 即待删除节点右子树的最小节点
                // 用这个节点顶替待删除节点的位置
                Node successor = minimum(node.right);
                successor.right = remove(node.right, successor.key);
                successor.left = node.left;

                node.left = node.right = null;

                retNode = successor;
            }
        }
        //判断retNode是否为空
        if(retNode == null){
            return null;
        }
        //维护retNode的平衡
        //更新height
        retNode.height = 1 + Math.max(getHeight(retNode.left), getHeight(retNode.right));

        //计算平衡因子
        int balanceFactor = getBanlanceFactor(retNode);

        if (Math.abs(balanceFactor) > 1) {
            System.out.println("unblanced:" + balanceFactor);
        }
        //维护平衡
        // LL 和 RR 型
        if (balanceFactor > 1 && getBanlanceFactor(retNode.left) > 0) {
            return rightRotate(retNode);
        }
        if (balanceFactor < -1 && getBanlanceFactor(retNode.right) <= 0) {
            return leftRotate(retNode);
        }
        //LR
        if (balanceFactor > 1 && getBanlanceFactor(retNode.left) < 0) {
            retNode.left = leftRotate(retNode.left);
            return rightRotate(retNode);
        }
        //RL
        if (balanceFactor < -1 && getBanlanceFactor(retNode.right) > 0) {
            retNode.right = rightRotate(retNode.right);
            return leftRotate(retNode);
        }
        return retNode;
    }

    public static void main(String[] args) {

        System.out.println("Pride and Prejudice");

        ArrayList<String> words = new ArrayList<>();
        if (FileOperation.readFile("pride-and-prejudice.txt", words)) {
            System.out.println("Total words: " + words.size());

            BST<String, Integer> map = new BST<>();
            for (String word : words) {
                if (map.contains(word)) {
                    map.set(word, map.get(word) + 1);
                } else {
                    map.add(word, 1);
                }
            }

            System.out.println("Total different words: " + map.getSize());
            System.out.println("Frequency of PRIDE: " + map.get("pride"));
            System.out.println("Frequency of PREJUDICE: " + map.get("prejudice"));
        }

        System.out.println();
    }
}
